Recovery of hydrocarbons from gases containing constituents, such as diolefines and the like



Patented Apr. 9, 1935 GASES CONTAINING CONSTITUENTS,

SUCH AS DIOLEFINES AND THE LIKE Willy Herbert, Frankfort-cn-thc-Main,

, I Germany, assignor to American Lurgl Corporation, New York, N. Y., a corporation of New York 1 No Drawing. Application December 7, 1932, Serial No. 646,213. In Germany December 21,

11 Claims.

The present invention relates to the recovery of hydrocarbons from gases containing constituents, such as diole flnes and the like, which are capable, as the result of polymerization or resini- 5 flcation, of exerting an injurious influence on the adsorptive media (such as active carbon, silica gel and the like) employed.

It is known that, in the recovery of benzol, for example, from coal gas under the usual working conditions of gasworks practice, and with the employment of active carbon as adsorptive medium, a decrease in the adsorptive efficiency of the carbon can be observed after a certain amount of benzol has been recovered.

This circumstance is attributable to the deposition of certain substances which, by reaction with the substances with which they are laden, by polymerization or by further transformation, act injuriously on the working efliciency of the adsorptive media. It was assumed, that the extent of the reduction of the adsorptive efliciency is dependent on the amount of gas passed, or the constituents deposited therefrom, and that, in maintaining the conditions determined by the plant as a whole, especiallywlth regard to the pressure and rate of flow of the gas, the consumption. of adsorptive media could be expected to depend on the quantity of the substances adsorbed.

It has, however, beenascertained in accordance with the present invention that the resiniflcation phenomenon does not depend on the amount of the gases passed-through the adsorptive media, but is substantially a function of time, inasmuch as the resinification of the substances liable thereto leads to the formation of products that are increasingly diiiicult to expel, the longer the substances have the opportunity of remaining in contact with the adsorptive media. In-

other words, ifin the treatment of a certain gas mixture, such as petroleum refinery gases, the

gases are contacted with theadsorbent and the ,adsorbed material is allowed to remain in contact with the adsorbent for several hours before being expelled in the regeneration process, av

clogging of the adsorbent is avoided and its adsorptive eiiiclency is preserved;

The result of this recognition is that, by taking care to minimize the duration of contact between the resiniiiable substances and the adsorptive media, the output eiiiciency of such plants can'be'improved. v

r In carrying the present invention into practical effect the amount of'adsorptive media employed in a plant of a given capacity is reduced below the usual level, so that, in consequence,

the proportion of adsorptive medium to the amount of the hydrocarbons contained in the gases to be treated per diem, is smaller than corresponds to the usual minimum ratio 2:1. The further that proportion is reduced, the better for the purpose in view. In practice, proportions of 1.5:1-and. preferably still smaller for instance, between 1:1 and 0.1:lcan be employed with advantage. In other words, if, for example,

the amount of adsorptive media hitherto employed for. the recoverable hydrocarbons was about 2000 kgs. of carbon per 1000 kgs. of recoverable hydrocarbon 'per diem, the amount ofcarbon employed according to the process of the present invention will be, for example, 1500 kgs., or preferably still smaller, such as 100-500 kgs.

In the treatment of'bydrocarbons from distillation plants, refinery gases and such gases as result from the decomposition or cracking of oils, the specified relative proportions can be applied, with particular advantage by increasing the velocity of flow of the gases through the adsorptive media.

In itself, an increase in the rate of passage of the gases under treatment, would be open to the objection that it would entail certain not' unimportant modifications in the operative conditions as compared, fcr'example, with those of-ordinary gasworks practice. For example, the introduction ofhigh velocities must,'in most instances, be accompanied by the provision of especial blower. It has, however, transpired that such objections, although capable of being primarily urged against increasing the velocity of the gases, neces-w sarily fall out of consideration in the faceof the considerable advantage resulting,.1ln particular,

from .the important increase in the efiiciency of the adsorptlve medium, and from therpossibility of reducing. the-size of the whole plantin conse-.

quence of the increased velocity of the gases.

The extent by which the period of contact.be-

tween the gases, or theadsorbed substances; and

the adsorptive medium can be shortened by increasing the rate of flow, or in any other way, such as by reducing the depth of the adsorptive layer to less than 1 meter and preferably less than 0.7

. meter, and also, if desired, by reducing the grainsize of the adsorptive medium at the same time to less than 3 mm.-whilst maintaining the rate of flow, or the like, at a normal level, not exceeding that hitherto employed-depends, in detail, on the amount and nature of the substances to be precipitated, and on other operative conditions.

In general, velocities exceeding 12 cms. per second, and especially those between 15 and 80 cms. per second-preferably 20 to 40 cms. per second-have been found suitable. Instead of increasing the rate of flow, however, the depth of the layer, accompanied by a reduction in the grain size of the adsorptive medium, may be reduced.

It is sometimes advisable to shorten, as far as possible, the period of exposure to the media, such as steam, employed for treating the laden adsorptive medium in order, for example, to expel the adsorbed substances, and therefore to minimize the length of the regenerative treatment, for example to less than three quarters of an hour, and preferably less than half an hour. The determinative factor is, in particular, the more or less complete prevention of the formation of resins and other polymerization products under the influence of high temperature and of the adsorptive, medium, which is generally catalytic, that is to say, to expel the adsorbed substances as rapidly as the other working conditions will admit, in order that the substances liable to resiniflcation may have the least possible opportunity of transformation.

The measures hereinbefore described maybe applied either singly or in combination.

In particular by following the prescribed working instructions, the output capacity of the plant and, for example, the number of steaming out operations the adsorptive material can undergo before becoming exhausted, can be increased thereby reducing the consumption of adsorptive media.

The following example illustrates the invention:

In a benzol recovery plant in which 300,000 cbm. of gas containing 1000 kg. of benzol are to be treated each day, it has previously been the practice to use two adsorbers, each containing 1200 kg. of active carbon. The active carbon has an adsorptive capacity at the start of 21% so that each adsorber at each cycle recovers about 250 kg. of benzol. Thus the two adsorbers recover about 500 kg. of benzol at each cycle and it is necessary to carry outtwo cycles per day in order to recover the whole 1000 kg. of benzol. Each cycle then takes 12 hours. In the operation of, this process the adsorptive capacity of the active carbon is reduced in 200-300 cycles from its original 21% to about 5% when it must be discarded. The ratio of adsorbent to material recovered in this process is 2.4 to 1.

In accordance with the present invention the process is carried out as follows: Theadsorbers are charged with only 200 kg. of active carbon each. This carbon has anadsorptive capacity of 21% so that about 42 kg. of benzol is recovered at each cycle of each adsorber. In order to recover the 1000 kg. of benzol each adsorber must therefore operate about 12 cycles per day so that each cycle of charging and regeneration isabout 2 hours instead of 12 hours as in the prior procsee. In this short time the polymerizable adsorbed substances either do not polymerize or do not polymerize sufllciently to deposit on the active carbon. and reduce its emciency. The ratio of :process is 0.4 to 1.

I claim:

1. A process for the recovery of hydrocarbons from gases containing substances with a tendency to polymerize, which comprises passing said gases through solid adsorptive media and reducing the proportion of said adsorptive media used to the amount of hydrocarbons recoverable from the gases under treatment per day to below 2:1.

2. A process for the recovery of hydrocarbons from gases containing substances with a tendency to polymerize, which comprises passing said gases through solid adsorptive media and reducing the proportion of said adsorptive media usedto the amount of hydrocarbons recoverable from the gases under treatment per day to not more than 1.5; 1.

3. A process for the recovery of hydrocarbo from gases containing substances with a tendency to polymerize, which comprises passing said gases through solid adsorptive media and reducing the proportion of said adsorptive media used to the amount of lwdrocarbons recoverable from the gases under treatment per day to between 1:1 and 0.1: 1.

4. A process for the recovery of hydrocarbons from gases containing substances with a tendency to polymerize, which comprises passing said gases through active carbon, and reducing the proportion of said adsorptive media used to the amount of hydrocarbons recoverable from the gases under treatment per day to below 2:1.

5. A process for the recovery of hydrocarbons from gases containing substances with a tendency to polymerize, which comprises passing said gases through silica gel and reducing the proportion of said adsorptive media used to the amount of hydrocarbons recoverable from the gases under treatment per day to below 2:1.

6. A process for the recovery of hydrocarbons from gases containing substances with a tendency to polymerize, which comprises passing said gases through solid adsorptive media with a velocity of above 20 cms. per second and reducing the proportion of said adsorptive media used to the amount of hydrocarbons recoverable from the gases under treatment per day to below 2:1.

7. A process for the recovery of hydrocarbons from gases containing substances with a tendency to polymerize, which comprises passing said gases through shallow layers of solid adsorptive media below 1 meter in depth with a velocity of above 20 cms. per second and reducing the proportion of said adsorptive media used to the amount of hydrocarbons recoverable from the gases under treatment per day to below 2:1.

8. A process for the recovery of hydrocarbons from gases containing substances with a tendency to polymerize, which comprises passing said gases through shallow layers of solid adsorptive media below 0.7 meters in depth with a velocity of above 20 cms. per second and reducing the proportion of said adsorptive media used to the amount of hydrocarbons recoverable from the gases under treatment per day to below 2: 1.

9. A process for the recovery of hydrocarbons from gases containing substances with a tendnecy to polymerize, which comprises passing said gases through shallow layers of solid adsorptive media below 1 meter in depth of reduced grain size, smaller than 3 mms. with a velocity of above '20 cms. per second and reducing the proportion of hydrocarbons recoverable from the gases under treatment per day to below 2:1.

11. A process for the recovery of hydrocarbons from gases containing substances with a tendency to polymerize, which comprises passing said gases through shallow layers or solid adsorptive media below 1 meter in depth and using a regenerative period of less than 30 minutes for the 'adsorptive media and reducing the proportion of said adsorptive media used to the amount of hydrocarbons recoverable from the gases under treatment per day to below 2:1.

wrLLY HERBERT. 

